Re: Re[2]: [mad-dev] III_requantize() accuracy

On Mar 24, 2004, at 5:36 PM, Grigory A. wrote:

...

Keeping in mind that 2^(-36.75) = 2^(-36) × 2^(-3/4), you will find that III_requantize(210, -147) calculates:

          210^(4/3)    ⇒ 0x04e0393e × 2^12

0x04e0393e × 2^(-36+12) ⇒ 0x00000005 2^(-3/4) ⇒ 0x09837f05 0x00000005 × 0x09837f05 ⇒ 0x00000002

Yes I am agree. Only one difference in my calculation scheme I firs multiply on root - in this case 2^(-3/4) and next rounding and shifting. This small changes give more precise result.

You make a good point. The accuracy can indeed be improved by multiplying the root first, before losing significant digits from the shift.

This probably merits a change for the next release.

Thanks,